[SOLVED] New to OOP

Archadian · October 3, 2008

I am getting this error and don't know why. I am new to OOP and trying to learn the language. If anyone has any tips or some easy way to learn it would be very much appreciated. Here is the error:

Warning: Missing argument 1 for Message::Message(), called in F:\Inetpub\wwwroot\ooptest.php on line 15 and defined in F:\Inetpub\wwwroot\oop.php on line 8

And here is the code:

ooptest.php

<html>

<head>

<title>The Cabal Online Guide</title>

</head>

<body>

<?php

include('oop.php');

$message = "Test Message!"; //Line 15

$mess =& new Message;
$mess->body($message);
$see = $mess->body();

echo "<table align=\"center\" valign=\"middle\" cellspacing=\"0\" cellpadding=\"0\" border=\"0\" height=\"45\">";

echo "<tr>";
echo "<td align=\"center\" width=\"589\" height=\"45\" border=\"0\">" . $see . "</td>";
echo "</tr>";

echo "</table>";

?>

</body></html>

oop.php

<?php

class Message
{

var $message = '';

function Message($body){  //Line 8

	$this->message = $body;

}

function body(){

	return $this->message;

}

}

?>

Archadian · October 3, 2008

No one knows what is wrong here?

KevinM1 · October 3, 2008

Well, there are several things at play here.

First, you don't initialize your object correctly. You should write:

$mess =& new Message($message);

Why? Because of your constructor:

	function Message($body){  //Line 8

	$this->message = $body;

}

Since you defined a constructor for your object, it's expecting you to pass to it the one parameter defined in its signature ($body). Even if you didn't define your own constructor, you'd still need to instantiate the object like so:

$mess =& new Message();

Object creation always invokes an object constructor, which, in turn, is a function. Since it's a function, you need the parentheses.

The next line follows the same train of thought from the previous mistake. Your body() function merely returns a value. It doesn't set the $message member of the object. So, trying to use it in that context doesn't make sense. Instead, you'll need to write what's commonly called a 'setter' function to go along with your 'getter' function. Together, they'd look something like this:

function getMessage()
{
   return $this->message;
}

function setMessage($message)
{
   $this->message = $message;
}

Using these within the client code would look like:

$myMessage = "Welcome to Rapture";
$welcome =& new Message($myMessage);

echo "$welcome->getMessage()";

$welcome->setMessage("Don't let the Big Daddy's get you");

echo "$welcome->getMessage()";

Finally, if you're serious about trying OOP with PHP, you should really update to PHP 5. I cannot stress how much better its OOP capabilities are.

DarkWater · October 3, 2008

Where did you get this OOP code, might I ask? It's using old, PHP4 OOP syntax. I'll explain why it errored out after, but for now, change your class to:

<?php

class Message
{

protected $message;

public function __construct($message) {

	$this->setMessage($message);

}

public function getMessage() {

	return $this->message;

}

public function setMessage($message) {
	if (strlen(trim($message)) == 0) {
		throw new Exception('Blank message given.');
	}
	$this->message = $message;
}
}

?>

I added some new things in there, but hopefully you get the idea and can learn a bit. Now, change your main file to:

<html>

<head>

<title>The Cabal Online Guide</title>

</head>

<body>

<?php

include('oop.php');

$message = "Test Message!";

$mess = new Message($message); //pass in $message in the constructor!!!

$see = $mess->getMessage();

echo "<table align=\"center\" valign=\"middle\" cellspacing=\"0\" cellpadding=\"0\" border=\"0\" height=\"45\">";

echo "<tr>";
echo "<td align=\"center\" width=\"589\" height=\"45\" border=\"0\">" . $see . "</td>";
echo "</tr>";

echo "</table>";

?>

</body></html>

Tell me if those changes were confusing. The reason your code was failing was because you defined an argument ($message) in the function header for the constructor, but you never passed one in. And yeah, where are you getting this OOP code? You'll want to learn how to use the new, better OOP system.

DarkWater · October 3, 2008

@Nightslyr: Actually, if an object's constructor takes no parameters, you can leave off the parens.

KevinM1 · October 3, 2008

@Nightslyr: Actually, if an object's constructor takes no parameters, you can leave off the parens.

Oh, really? Interesting. Eh, I still like the parens...it matches the rest of my coding style.

Archadian · October 3, 2008

I have php 5 installed. I am just new to OOP so im not familiar with anything yet. Functions i can do in PHP...OOP is a work in progress. I actually wrote this myself...didn't find it anywhere...just a simple OOP code. I am a "hands on" learner so i have to write code and do the whole trial and error thing. Thanks for the help.

Archadian · October 3, 2008

Also...any online tutorials on the new OOP (PHP 5) syntax? Or any books I can buy?

xtopolis · October 4, 2008

http://www.phpfreaks.com/tutorial/oo-php-part-1-oop-in-full-effect

http://www.phpfreaks.com/tutorial/oo-php-part-2-boring-oo-principles

http://www.phpfreaks.com/tutorial/oo-php-part-3-uml-classes-and-relations

Archadian · October 4, 2008

I have another question for learning purposes. Can anyone tell me what is wrong with this code? Hopefully someone can help me out. Thanks in advance.

class.php

class Mysql
{

protected $host = '';
protected $user = '';
protected $pass = '';
protected $result;
protected $db;

public function __constructor($host, $user, $pass, $db) {

	$this->host = $host;
	$this->user = $user;
	$this->pass = $pass;
	$this->result = $result;
	$this->db = $db;

}
public function web() {

mysql_connect($this->host, $this->user, $this->pass) or die("Connection to the website DB failed.");
$this->result = mysql_select_db('db') or die("Selecting the DB failed.");
return $this->result;

}

public function forums() {

	mysql_connect($this->host, $this->user, $this->pass) or die("Connection to the forums DB failed.");
	$this->result = mysql_select_db('db') or die("Selecting the DB failed.");
	return $this->result;

}

}

and here is the code on the index.php

$db =& new Mysql($host, $user, $pass);
$this->web();

I know its wrong so if someone could help me out and let me know what i need to do or change i would appreciate it. Thanks.

xtopolis · October 4, 2008

You need to make it say:

$db->web();

"this" should only be used inside a class, afaik

JasonLewis · October 4, 2008

If you wish to pass a blank argument you can do so by setting it in the constructor.

public function __constructor($host, $user, $pass, $db="")

DarkWater · October 4, 2008

It should be __construct, not __constructor.

JasonLewis · October 4, 2008

Ha! Indeed it should. Didn't even notice that one.

Archadian · October 4, 2008

__construct doesn't work. on the other hand __constructor works great

DarkWater · October 4, 2008

__construct doesn't work. on the other hand __constructor works great

__construct is called automatically when a class is created, trust me.

Sign In

[SOLVED] New to OOP

Recommended Posts

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Join the conversation

Important Information